Drottningholm Palace \'drut-niq- 1 h6lm\ Royal palace, near Stock¬ holm, Sweden. It was designed by Nicodemus Tessin (1615-1681) and built 1662-86. It shows French Baroque influences in its plan, gardens, and interior, but it also has Italian Classical elements and is capped by a Nordic sateri roof. A theater attached to it was built in the 1760s and is preserved with its original sets and stage machinery as a theatrical museum. The palace was formerly the Swedish royal family’s summer residence.
drought Lack or insufficiency of rain for an extended period that severely disturbs the hydrologic cycle in an area. Droughts involve water shortages, crop damage, streamflow reduction, and depletion of ground- water and soil moisture. They occur when evaporation and transpiration exceed precipitation for a considerable period. Drought is the most seri¬ ous hazard to agriculture in nearly every part of the world. Efforts have been made to control it by seeding clouds to induce rainfall, but these experiments have had only limited success.
drug Any chemical agent that affects the function of living things. Some, including antibiotics, stimulants, tranquilizers, antidepressants, analgesics, narcotics, and hormones, have generalized effects. Others, including laxa¬ tives, heart stimulants, anticoagulants, diuretics, and antihistamines, act on specific systems. Vaccines are sometimes considered drugs. Drugs may protect against attacking organisms (by killing them, stopping them from reproducing, or blocking their effects on the host), substitute for a miss¬ ing or defective substance in the body, or interrupt an abnormal process. A drug must bind with receptors in or on cells and cannot work if the receptors are absent or its configuration does not fit theirs. Drugs may be given by mouth, by injection, by inhalation, rectally, or through the skin. The oldest existing catalogue of drugs is a stone tablet from ancient Baby¬ lonia (c. 1700 bc); the modern drug era began when antibiotics were dis¬ covered in 1928. Synthetic versions of natural drugs led to design of drugs based on chemical structure. Drugs must be not only effective but safe; side effects can range from minor to dangerous (see drug poisoning). Many
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574 I drug addiction ► dry ice
illegal drugs also have medical uses (see cocaine; heroin; drug addiction). See also drug resistance; pharmacology; pharmacy.
drug addiction or chemical dependency Physical and/or psy¬ chological dependency on a psychoactive (mind-altering) substance (e.g., alcohol, narcotics, nicotine), defined as continued use despite knowing that the substance causes harm. Physical dependency results when the body builds up a tolerance to a drug, needing increasing doses to achieve the desired effects and to prevent withdrawal symptoms. Psychological dependency may have more to do with one’s psychological makeup; some people may have a genetic tendency to addiction. The most common addictions are to alcohol (see alcoholism), barbiturates, tranquilizers, and amphetamines, as well as to the stimulants nicotine and caffeine. Initial treatment (detoxification) should be conducted with medical supervision. Individual and group psychotherapy are critical elements. Alcoholics Anonymous and similar support groups can increase the success rate of other efforts. The ability to admit addiction and the will to change are necessary first steps.
drug poisoning or medicinal poisoning Harmful effects of drugs, from overdose or sensitivity to regular doses. Many medicines are dangerous; the margin between dose and overdose is often narrow. A nor¬ mally safe dose may be toxic in some people, over time, or in combina¬ tion with certain foods, alcohol, or other drugs. Safeguards to prevent drug poisoning include testing in animals, then human volunteers, and then patients. Drugs unsafe for self-medication are available only to doctors or by prescription. Pharmacists advise the public on proper use.
drug resistance Property of a disease-causing organism that allows it to withstand drug therapy. In any population of infectious agents, some have a mutation that helps them resist the action of a drug. The drug then kills more of the nonresistant microbes, leaving the mutants without com¬ petition to multiply into a resistant strain. This situation is more likely if the drug is not taken properly (e.g., a course of antibiotics not completed, anti-HIV drug doses missed) or not prescribed properly (e.g., an antibi¬ otic given for a viral disease). Resistance factors can also be transferred between species that infect the same body. The overprescription of anti¬ biotics in humans and the addition of antibiotics to animal feed have accelerated the evolution of resistant strains of bacteria, making it increas¬ ingly difficult to fight off certain disease-causing organisms.
Druid Member of a learned class of priests, teachers, and judges among the ancient Celtic peoples. The Druids instructed young men, oversaw sacrifices, judged quarrels, and decreed penalties; they were exempt from warfare and paid no tribute. They studied ancient verse, natural philoso¬ phy, astronomy and religious lore; their principal doctrine was belief in the immortality of the soul and the transmigration of souls. They some¬ times practiced human sacrifice to cure gravely ill people or protect war¬ riors in battle. The Druids were suppressed in Gaul by the Romans in the 1st century ad and in Britain a little later. They lost their priestly func¬ tions in Ireland after the coming of Christianity but survived as poets, historians, and judges. See also Celtic religion.
drum or croaker In biology, any of about 160 species (family Sci- aenidae) of carnivorous, generally bottom-dwelling fishes. Most are marine, found along warm and tropical seashores. Most can “vocalize” by moving strong muscles attached to the air bladder, which acts as a resonating chamber, amplifying the sounds. Drums have two dorsal fins and are usually silvery. The weakfishes, sea trouts, and squeteagues (genus Cynoscion ) have a large mouth, jutting jaws, and canine teeth, but most drums have an underslung lower jaw and small teeth. The largest species, the totuava, weighs up to 225 lbs (100 kg), but other species are much smaller. Many drums are food or game fishes. See also bass, kingfish.
drum Musical instrument, the sound of which is produced by the vibra¬ tion of a stretched membrane. Drums are usually either cylindrical or bowl-shaped. The drum is a universal instrument and very ancient; a drum dating to 6000 bc has been found in Moravia. Drums have been impor¬ tant ritually in cultures worldwide. They may have a definite pitch or be unpitched; those of Africa, South and Southeast Asia (see tabla), and the Middle East are mostly pitched, whereas Western drums are more often unpitched. Drumming has attained its highest degree of development in Africa and India. From the 13th century, the folk dance in Europe was accompanied by a single musician playing simultaneously the pipe or fife and the tabor, a small double-headed snare drum played with one stick. The side drum, or snare drum, has coiled wires or gut strings strung across the lower head, which vibrate against it when the upper head is struck.
The powerful bass drum is used especially in marching bands. The pitched timpani are the standard orchestral drums. Until the 17th cen¬ tury, drum parts in Western music were entirely improvised. The drum set used in popular music is played by a single person and normally includes a snare drum, tom-toms, a pedal-operated bass drum, and sus¬ pended and hi-hat cymbals.